Control system for hydraulic presses



`lune 3, 1941. f R. DiNzL 4 2,244,420

CONTROL SYSTEM FOR HYDRAULIC PRESSES Filed April 21, 1938 5 Sheets-Sheet 1 June 3,1941. R, W, DMLl 2,244,420

CONTROL SYSTEM `FOR HYDRAULIC PRESSES ATTO R N EYS June 3, 1941.

R. w. DlNzL 2,244,420

CONTROL SYSTEM FOR HYDRAULIC PRESSES Filed April 21`, 1938 3 Sheets-Sheet 3 ATTORNEYS Patented June 3, 194i CONTROL SYSTEM FOR HYDRAULIC PRESSES Richard W. Dinzl, Westfield, N. J., assignor to The Watson-Stillman Co., Roselle, N. J., 'a corporation ,of New Jersey Application April 21, 1938, Serial No. 203,301

4 Claims.

This invention relates more particularly to improvements in press apparatus of the type wherein a reciprocable press head is advanced on a Working stroke by a hydraulically operated mechanism and, after completion of the pressing operation,' is retracted automatically by another hydraulically operated mechanism, the operation of said mechanisms being controlled by a'hydraulic circuit including a pump. Usually, in such an apparatus, a complicated and costly pump of a variable delivery, or variable stroke,

type has been required to supply the said advanc- Other objects of the invention will appear hereinafter,

In the drawings,

Fig. 1 is a diagrammatic sectional view of the press apparatus, with the reciprocable' press head in retracted position and with the control system in condition to maintain/the press head idle;

Fig.`2 is a view similar to Fig. l, with the control system in condition to cause advance of the reciprocable press head and .with the latter advanced suiciently to commence the pressing operation, and

Fig. 3 is a view similar to Figs. 1 -and 2, withl the reciprocable press head advanced suiiiciently to complete the pressing operation, and with parts of the control system positioned to cause retraction of the press head.

My improved control system is shown in connection with a press having a lixed lower press head and a reciprocable upper press head 2.

-The head 2 has an upwardly extending ram 3 reciprocable in a xed, vertical hydraulic cylinder l. A surge tank 5 is mounted upon the upper end of said cylinder and is in valved communication therewith. Hydraulic push-back mechanism isprovided to retract, or elevate. the press head 2. rams vor plungers 6 borne by the press head 2 and reciproca-ble 'in xed, vertical, hydraulic cylinders 1.

The main press cylinder 6 is formed with a This mechanism includes depending central tubular extension 8 depending from its upper end and extending into a central cylindrical recess 9 in the r'am 3.' Said tubular extension has a close sliding t in the upper end of recess 9 and it serves to conduct hydraulic pressure to the bottom area Ill of the recess. An upper end area Il of the ram, surrounding the tubular extension 8, is subject to the fluid pressure admitted to the main cylinder. The surge tank communicates with the bore of the tubular extension 8 through a port 4I2 and communicates with the cylinder l through a 'port I3. Downwardly opening surge valves I4 and I5 control flow through the ports |2 and I3 respectively. These valves are hydraulically operated. Each has anupwardly extending stem bearing a piston I6 working in a small iixed cylinder Il. By admission of hydraulic Apressure to these cylinders the valves are opened and closed, as will be explained hereinafter.

A constant delivery pump I8 supplies hydraulic pressure for operating the mechanisms for advancing and'retracting the press 4head 2. This pump is shown diagrammatically. It may be of a simple conventional type and it iscOntinuously power driven while the press head is being moved and also while it is. idle between pressing operations. A pipe IS conducts uid from the surge tank -to the pump inlet.- Preferably the uid is oil. A discharge pipe leads fromv the pump outlet, is connected to a pipe 2| and has a check valve 22 opening toward the latter pipe. From pipe 2| a pipe 23 leads to a main control valve device 2l. One end of pipe 2| is connected to a hydraulic pressure accumulator 25 and the opposite end of the pipe is connected to an auxiliary valve device 26. From a point between the pump and check valve 22 a pipe 2l leads from the pump discharge pipe 20 to a valve device 28 for bypassing the pump discharge back to the surge tank, as will be explained hereinafter. A safety valve device 29 is also connected to pipe 2l at an intermediate point. Y

The accumulator 25 is of a hydro-pneumatic type. A plunger 30 has one end reciprocable in a hydraulic pressure cylinder 3|. The.. opposite end of the plunger bears a piston 32 of liberal diameteritted to reciprocate in an air cylinder 33. A supply pipe 34 leads to the outer end of the air cylinder and has a -power driven air pump 35 and am air storage Atank 36 connected thereto for maintaining a constant pneumatic pressure upon the outer face of piston 32. This pressure urges the plunger 30 into the hydraulic cylinder 3| to exert pressure upon the oil therein.

Main control valve device 24 comprises a vertical cylindrical casing 31 within which a doubleheaded piston valve 33 is tted to reciprocate.

-branch piping connecting it to the lower ends of the push-back cylinders 1. Pipe 43 also has branch piping 43* connectingit to the upper ends oi the small surge valve cylinders I1. 'I'he control vvalve has a stem 4I extending from opposite ends of the casing. The upper endl portion of said stem forms a core for a solenoid coil 42. At 43 a vertical extension rod 44 is joined to the lower end of the valve stern, extends downwardly pipe 6l vthrough a branch pipe 63. The latter has a spring-loaded valve device 13 to resist now to cylinder 64. Return branch piping 1I leads from -pipe 63 and cylinder 64 back to pipe 63. This piping by-passes the valve device 13 and has a check valve 12 opening toward pipe 63.

Pipe 32, which leads from auxiliary valve device 53, is connected to a. pipe 13. One end of pipe 13 leads toi the main press cylinder 4 fordelivery oi pressure to act upon the ram surface Il. The opposite end of pipe 13 is connected to a pressure hunting device 14. A branch pipe 'Il leads from pipe 13 to the lower end si the small cylinder I1 associated with surge valve I5. Another branch pipe 16 leads from pipe 13 to pipe y 63 and has acheck valve 11 opening toward the to a point near the lower press head and is cohnected to a lever 45 for manual operation of the control valve when desired. At a point below the surge tank, rod 44 bears an adjustable abutment 46, and a spring 41 acts upon said abutment to constantly urge the rod and the control valve downwardly. borne by the rod for vertical adjustment thereon and is engageable by an abutment 43. borne by* the reciprocable press head, to force the rod 1nd the control valve upwardly when the press head rises to a certain height.

Auxiliary valve `device 23 includes a casing forming two end to end cylinders 63 and 5I. I A double-headed piston valve 62 is iitted to reciprocate in cylinder 50 and has a stem 53 extending into cylinder 5I and bearing a piston 54. A spring 55 is interposed between piston 64 and the upper end of cylinder 6I and constantly urges said piston and the valve downwardly, with reference to.. the drawings. The piston and valve are forced upwardly against the resistance of the spring by admission of iluid pressure from pipe 40 through a branch pipe 56 to the lower end of cylinder 5I. Reciprocation of the valve opens. and closes communication between pipe 2l and the interior of cylinder 53, and also between the interior of said cylinder and a. discharge pipe 61 directed to discharge into the surge tank: A pipe 58 leads from cylinder 63, at a point between the valve heads, and is connected to another auxiliary valve device 53. A branch pipe 63 leads from pipe 53 to the upper end of the bore in the tubular extension 8 oi the main press cylinder.

A branch pipe 6I also leads from the pipe 63 to the lower end of small cylinder I1 associated with the surge valve I4. Pipe 63 also has other branches whose purpose will be explained hereinafter.

Another abutment 43 is,

` forms a core for a solenoid coil 34'.

latter.

The pressure limiting device 14 includes a cylinder 13 into one end of which the pipe 13 opens. A piston 13 Viltted to reciprocate in said cylinder has a stem extending from the opposite end of the cylinder and bearing an electrical switch element 33. Reciprocation of piston 13 and switch member 33 eiects circuit opening and closure as will be described hereinafter. A spring 3| constantly urges the piston toward the end of the cylinder to which pipe 13 is connected.

The valve device 23 `ior by-passingl the pump discharge includes a cylindrical casing 32. A 'piston valve 33 is fitted to reciprocate in the cylinder and has a stem 34 projecting from the opposite ends of the cylinder. At one end of the cylinder there is a-spring li'acting upon the valve stem to constantly urge the valve to close communication between pipe 21 and a discharge pipe 36 directed to discharge into the surge tank. 4The opposite end portion of the valve 4stern 34 By energizing said coil the valve is shifted to open communication between pipes 21 and 33.

The operation of the main control valve device 24 and the operation of the pump by-pasa valve device are controlled by an electrical system. This system. includes manually operable push button switches 31 and 33, switches 33 and 33 operable by reciprocation of the accumulator plunger 33, the switch element 33, relays 3| and 33, line wires L and L and wiring which will be traced in the following description of the operation of thepress apparatus.

Assume that the various parts of the apparatus are in the positions shown in Fig. 1. except that by-pas's valve 33 is in position to close ccmmunication between pipes 21 and 36, the accumulator plunger is elevated and the relay 33 is open. Thenthe pump I3 will charge thev accumulator by drawing oil from the surge tank through pipe I3 and discharging the oil through Auxiliary valve device 53 is similar to valve de- A vice 26 vin structure except that it controls communication only between pipe 53 and a pipe 62. f

. It includes a casing forming end t'o end cylinders 63 and 64. A double-headed piston valve 65 is fitted to reciprocate in cylinder 63 and has a stem 66 extending into cylinder 34 and bearing a piston 61. A spring 63 1constantly urges piston 61 and valve 65 downwardly, with reference to the drawings, to close communication between pipes 53 and 62. The piston and valve are forced upwardly against the resistance of the spring to opencommunication between pipes 58 and 62 by admission of hydraulic pressure tothe lower end of cylinder 64. Said pressure is admitted from pipes 23 and 2| to the cylinder 3| of the accumulator.' As hydraulic pressure is built up in the latter it will overcome the pneumatic pressure l'at the under side of piston .32 and force the plunger 33 downwardly. When the accumulated pressure-reaches'the maximum permissible limit it will iorce the plunger down to the position `*shown in Fig. 1. In that position the plunger eil'ects closure of switch 83. The latter is normally spring-urged to open position. It is closed by engagement of an arm 94 borne by the accumulator plunger.

Switch 33 closes a circuit including line wire L, conductor 35, the armature of relay 33, conductor 96, switch 83, conductor 31, the winding of relay 33, conductor 36 and line wire L'. Current through said relay winding closes relay 33 and thereby a circuit is established including, as shown in Fig. 1, line wire L, conductor 95. the armature of relay 93, conductor 99, conductor I 09, solenoid coil 84', conductor IDI and line wire L'. Current through coil 84' causes shiftof the valve 83 to open communication between pipe 21 and pipe 85 to thereby by-pass the pump discharge to the surge. tank. The relay 93 is retained closed by a holding circuit including line wire L, conductor 95,the armature of relay 93,- conductors 99 and |00, switch 90, which is normally springheld in closed position, conductor 91, the winding of relay 93, conductor 98 and line wire L. Thereby, valve 83 is held open to by-pass the pump discharge until the arm Elli,` by rise of the accumulator plunger, engages and opens the switch 90. That breaks said holding. circuit so that the relay 93 opens and breaks the circuit through solenoid 88'. Spring 85 then closes the pump by-pass valve so that the pump can recharge the accumulator.

As shown in Fig. 1, the press head 2 is held elevated by hydraulic pressure in the push-back cylinders 1, the pressure being trapped in said cylinders by the control valve 38 which is in position to close communication between pipe 40 from the push-back cylinders, and the discharge pipe 39.' The push-back pressure is transmitted from pipe 80 through the piping 40 to the upper ends of the small cylinders I1 so that the surge valves I4 and I5 are held open. At the same time, push-back pressure transmitted throughpipes 4U and 56 holds valve 52 up to shut oi admission of pressure from supply pipe 2| .to piping 58 and 60 leading to the area I0 of the ram 3. Since valve S5 is dependent upon pressure in pipe ,69 to open it and since pressure is shut off from said pipe, the Valve is held closed by its spring against admission of pressure to the main press cylinder through pipes 62 and 13.

If, while the parts are in the positions shown in Fig. l, the push-back pressure in cylinders 1 should leak Adown the press head will depress slightly and move the abutment 49 downward. 'I'hat will permit the spring 41 to shift the control valve downward to open communication between the pipe 23 and pipe 4I) so that the pump and the accumulator can restore the pressure in the push-back cylinders. Consequent rise of the press head 2 will cause the abutments 49 and G8 to restore the control valve to the Fig. 1

relay 9! establishes and holds a control valve operating circuit including a conductor III leading from conductor I of said holding circuit, the winding of solenoid 82, conductor II2 and line wire L. Energization of solenoid l2 raises control valve 38, against the resistance of spring 81 to a position for discharge of pressure from the push-back cylinders and admission of pressure for advancing the press head 2 downwardly.

As shown in Fig. 2 the upwardly shifted control valve 38 permits discharge from the pushback cylinders 1 through pipe MlA and pipe 39to the surge tank. 'I'hat permits the press head 2 to descend by gravity. During its descent it maintains pressure in the push-back cylinders and pipe 4l] and this pressure, through thepiping -40 and 40a to the cylinders I1, holds thefsurge valves open. Said pressure, acting through the piping 48 and 56, also holds the auiiiliary. valve 52 in the position shown in Fig. l to out off communication between the pressure supply pipe 2I and the piping 58 and 60 so'that the pump and the accumulator are cut oi from the press cylinder during said descent of the ram. When, however a die D borne by the press head 2 contacts with the work W borne by the press head I, and the resistance of the work is suicient to arrest descent of the head I, pressure in the push-back cylinders and in the connected piping 49 and 56 falls. Thereby the spring 55 is permitted to shift the auxiliary valve 52 'to the position shown in Fig. 3, and open communication between the pressure supply pipe ZI and the pipe 60 so that pump pressure and accumulator pressure are admitted to the bore of the tubular extension 8 in the press cylinder. Simultaneously, pressure is delivered by pipes 6I) and 6I to the lower endA of the small cylinder I1 associated with the surge valve I4. This pressure can close the surge valve since the pressure'for opening it is being relieved through piping 80 and 4I)a along with relief of push-back pressure. Closure of surge valve I4 renders the pressure admitted to the ram surface I0 eiective for the first portion of the pressing operation. Closing of surge valve I5 and admission of pressure to the main press cylinder to act against -ram surface il are delayed until the pressing operation has' progressed to a certain degree. -Then the pressure position and stop the upward movement of the press head.

Downward movement of press head 2 for a pressing Aoperation is caused by pressing -the switch 81. This switch is normally held by a spring in circuit-opening position. Pressure upon the switch shifts it to circuit-closing position. Switch 88 is normally held by a spring in circuit-closing position. Switch 81 is a starting switch and switch 88 is an emergency switch.

Pressing of switch 81 momentarily closes a circuitincluding line wire L, conductor 192, a normally closed switch I93, conductor 499, the armature of relay 9I, conductor |95, switch 81,

conductor |96, conductor Ill-'1, switch .88, -con-l duc-tor |98, switch element 8U, conductor |09, the winding of relay 9|, conductor iIIl and line wire L'. Said relay is closed thereby and establishes a circuit to hold it closed. AThis holding circuit includes, as shown in Fig. 2, line wire L, switch w3, conductor |88, the armature of relay 9|, conductor I01, switch 88, conductor I 98, switch element 8l), conductor-|99, the winding of relay 9i, conductor I IU and line wire L. The closed .build-up within the ram recess 9 registers'in pipes and 69, and when the pressure becomes suiicient it operates the spring-loaded valve device 18 for admission of pressure to cylinder 64 of auxiliarS7 valve device 59. The pressure admitted to cylinder 54 shifts valve 65 against the `resistance of spring 68 to admit pump and accumulator pressure from pipe 58 to pipe 62 and pipe 13. Pipe 13 leads to the main press cylinder 4, and its branch 15 leads to the lower end of the small cylinder i1 associated with surge valve I5. Pressure s o admitted to the small cylinder closes surge valve I5 so that the pressure admitted to the press cylinder can become eiective' against the ram surface II. Pressure supplied by the pump and the accumulator simultaneously then acts upon both ram surfaces I0 and II to force the press head 2 to complete the pressing operation.

When the hydraulic pressure acting upon the ram 3 reaches a maximum permissible limit, automatic retraction of the press head 2 is eected by the control system. Said maximum pressure 'is Vtransmitted through pipe 13 to the pressure There it shifts piston 19 'against the' resistance of spring 8l and moves switch element 8|! to break the electrical ccnnection between conductors |08 and |09. Since the previously described holding circuit for relay 8| is dependent upon said connection, breaking of the latter causes the relay to open and thereby open the circuit through solenoid 42 of the control valve. Spring 41 then shifts the control valve down to the position shown in Fig. 3.

In Fig. 3 the'control valve has just been shifted for press head retraction but the auxiliary valves 52 and 65 are still in position to cause the pressing operation. Their shift back to Fig. 1 position' is caused by said downward shift of control valve 38. The latter then admits pump pressure and accumulator pressure from pipe 23 to pipe 40 whichleads to the push-back cylinders 1. This pressure is also transmitted through pipe 56 for shifting )valve 52 to permit relief of pressure in the ram recess 9, through pipes 60 and 51 to the surge tank. Since pipe 13 is connected by pipe 16 to pipe 60, the pressure in the press cylinder 4 is also relieved through pipes 13 and 16, past check valve'1fl to pipe 60 and thence through valve device 26 tothe surge tank. The surge valves |4 and |5 are opened by relief of pressure in the lower ends of cylinders I1 through pipes 6| and 15 to the vented pipes 60 and 13 respectively, and admission of push-back pressure from pipe 40 through the piping 40 to the upper ends of the small cylinders. It will be noted that there is exhaust of fluid from the press head advancing mechanism through the pipe 51 and also through the ports l2 and I3. This distribution of exhaust reduces turbulence in the surge tank. Venting of the press-headadvancing mechanism through the pipe 51 also assists opening 'of the surge valves by relieving operations of the press head 2. Therefore by opening this switch said circuits are disabled for control of the press operations by means of the hand lever 45.

What I claim is:l

1. A press apparatus having press head advancing mechanism' and press head retracting mechanism,.both operable by hydraulic pressure, a surge tank associated with said advancingl mechanism and pressure supply means to withdraw liquid from the surge tank for supply of hydraulic pressure to said mechanisms, the

advancing mechanism having an area subject to the pressure at the under side of the valves, tending to hold them closed. Y

Since the pipe 1I leading to the auxiliary valve device 59 is connected to the vented pipe 60, hydraulic pressure in cylinder 64 of said device will be relieved through pipe 1| and past check valve 12 topipe 60. 'I'hat will permit spring 68 to shift valve 55 to closed position cutting on communication between, pipes 58 and 52. Thereby said valve is resetfor another operation of the press. Relief nof pressure in the press head advancing mechanism relieves pressure also in the pressure-limiting device 14 through the pipe 13 and the aforesaid connections of the latter with the discharge pipe 51. The spring 8| can then shift the switch element back to the position shown in F18. 1. v

The relief of pressure in the press head advancing mechanism and the admission of preshydraulic pressure for a portion of the press head advance and lan area subject to hydraulic pressure for a following portion of the advance to augment the pressure on said first area, a surge valve to control communication between the surge tank and said first-area and, a surge valve to control communication between the surge tank and said second area, a main control valve device operable to admit pressure to the retracting mechanism andv exhaust it therefrom to the surge tank, an auxiliary control valve constantly urged to admit pressure from said supply means to the advancing mechanism and responsive to admission of pressure 'to the retracting mechanism to exhaust pressure from said first area of the advancing mechanism, the first surge valve having operating means responsive to said pressure admission by said auxiliary valve to close the surge valve, and a second auxiliary valve responsive to said pressure admission by the first auxiliary valve to admit pressure from the latter to said second area, the second surge valve having operating means responsive to the latter admission to close the surge valve, and said operating means for the two surge valves being responsive to pressure admission to the retracting mechanism to open the surge valves.

2. In a hydraulic press apparatus having presshead-advancing mechanism and press-head-retracting mechanism. both operable by hydraulic pressure, a hydraulic .pressure accumulator, a

. constant delivery pump having a receiving conto a predetermined degree of charging of the acsure to the retracting, or push-back mechanism.

causes elevation or retraction of the press head 2. Retraction continues until abutment 49 borne by the press head engages abutment 4l borne by valve-operating rod 44 and `causes shifting of the control valve 38 back to the position shown in Fig. 1. This shift is effected against the resistance of spring 41.

If it be desired to stop advance of the press head 2 and retract -it before completion-of its working stroke the emergency switch 88 ispress'ed to open the aforesaid holding circuit forv relay 0|. The latter then opens and breaks the cir- "cuit through'solenoid 42 of the main control `valve. Spring 41 can then shift the control valve 'downwardly, for press head retraction.

" `fItgwill be noted that switch |03 is included in all of .the circuits employed for controlling the cumulator to direct the pump discharge to said liquid source to limit charging of the accumulator, controll valve-means operable to admit hydraulic pressure toA -said retracting' mechanism and operable also to relieve hydraulic pressure in v the retracting mechanism, means responsive to relief of pressure. in the retracting mechanism to place said pump and accumulator in delivery communication4 with said advancing mechanism for performing a pressing operation, means responsive to pressure admitted to the retracting mechanism to relieve hydraulic pressure in said advancing mechanism for press head retraction, and means responsive to a predetermined hydraulic pressure in the advancing mechanism to operate said control valve means to cause said admission of hydraulic pressure from the pump and accumulator to the retracting mechanism, for press head retraction. I p

3. In a hydraulic press apparatus including press-head-advancing mechanism and presshead-retracting mechanism, both operable. by v f ing said auxiliary valve to place its said connections `in communication, hydraulic operating means for said auxiliary valve having a hydraulic connection with the retracting mechanism independent of the main control valve to operate the auxiliary valve against the resistance of said constant urging means to relieve hydraulic pressure in the advancing mechanism in response to build up of hydraulic pressure in the retracting mechanism, and operating means for the surge valveresponsive to build up of hydraulic pressure in the retracting mechanism to open the surge valve and responsive to relief of pressure in the retracting mechanism to close the surge valve, whereby relief of hydraulic pressure in the retracting mechanism through the main control valve will cause press head advance, and build up of hydraulic pressure 4in the retracting mechanism through the main control valve will cause press head retraction. f

4. A hydraulic press comprising in combina-V arate chambers therewith, pressure uid supply' means, including a constant delivery pump and an accumulator, for supplying pressure uid to said chambers to actuate said press plunger, iiuid storage means, two surge valves respectively associated with said chambers and adapted selectively to elect or interrupt hydraulic communication` between said chambers and said fluid storage means in response to the pressure conditions in said chambers, push back means for retractingsaid press plunger after completion of its working stroke, main valve means controlling the supply of pressure Aiiuid from said pressure :fluid supplyl means to said push back means and being-operable to connect said pushback means to an exhaust, while interrupting hydraulic communication between said push back means and said pressure iluid supply means.

,auxiliary valve means controlling the supply of uid from said uid supply means to one of said chambers, yielding means constantly urging said auxiliary valve means to eiect hydraulic com-.- munication between said one chamber and said fluid supplyl means, hydraulic operating means adapted in response to a predetermined push back pressure to counteract said yielding means so as to cause said. auxiliary valve means to relieve hydraulic pressure in said chambers to extion a two step hydraulically, operable press. y

plunger, a press cylinder operatively associated with said press plunger so as to form two sephaust, and controlling means adapted `'in cooperation with said auxiliary valve means to control the supplylo'f pressure uidirom said uid supply means to the 'other 'olsaid-two chambers in response to a predetermined pressure in said first mentionedl chamber.

RICHARD W. DINZL. 

